[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 312354
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI OCT 31 2008

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...THE ITCZ...
ITCZ AXIS IS ANALYZED ALONG 10N14W 11N23W 8N35W 9N50W 11N62W.
TWO SURFACE TROUGHS REMAIN EMBEDDED WITHIN THE ITCZ...ONE IS
JUST SOUTH OF THE CAPE VERDE ISLANDS ALONG 24W AND IS GENERATING
SCATTERED SHOWERS AND ISOLATED TSTMS. THIS TROUGH SHOWS UP ON
THE TPW PRODUCT FROM CIMSS WHERE A BULGE OF MOISTURE IS SEEN.
THE SECOND ONE IS ALONG 45W. A LARGE AREA OF DISORGANIZED
SHOWERS AND THUNDERSTORMS ACCOMPANIES THIS TROUGH AND COVERS
FROM 8N-14N BETWEEN 40W-48. UPPER DIFFLUENCE IS ENHANCING THIS
CONVECTIVE ACTIVITY. ELSEWHERE...ANOTHER LARGE AREA OF MODERATE
TO ISOLATED STRONG CONVECTION IS INLAND OVER WEST AFRICA FROM
8N-12N BETWEEN 10W-14W. SCATTERED MODERATE CONVECTION IS NEAR
6N22W...12N32.5W...AND WITHIN 115 NM N OF AXIS BETWEEN 34W-36W.

...DISCUSSION...

GULF OF MEXICO...
WEATHER CONDITIONS ACROSS THE GULF REGION HAVE EXPERIENCED
LITTLE CHANGE SINCE YESTERDAY. A SURFACE RIDGE ANCHORED ON A
1035 MB HIGH OVER THE CAROLINAS DOMINATES THE ENTIRE REGION. THE
RIDGE ALSO ENVELOPS THE W ATLANTIC...MUCH OF CUBA...THE NW
CARIBBEAN AND THE YUCATAN PENINSULA. COLD AIR STRATOCUMULUS
CLOUDS ARE NOTED OVER MUCH OF THE AREA. THE E GULF AND FLORIDA
PENINSULA IS DOMINATED BY MODERATE/STRONG SUBSIDENCE WHICH IS
LIMITING ANY DEEP CONVECTIVE ACTIVITY. NE WINDS OF 20 KT ARE
BLOWING OVER THE SE PORTION OF THE GULF DUE TO TIGHT PRES
GRADIENT BETWEEN THE ABOVE MENTIONED HIGH PRES AND LOWER PRES
OVER THE SW CARIBBEAN. THE REMAINDER OF THE GULF HAS WINDS OF 10
TO 15 KT. THIS HIGH PRES SYSTEM OVER THE CAROLINAS IS FORECAST
TO WEAKEN THROUGH THE WEEKEND ALLOWING WINDS TO DIMINISH ACROSS
GULF WATERS. ALOFT...A MAINLY ZONAL FLOW DOMINATES THE GULF BUT
THIS PATTERN IS EXPECTED TO CHANGE DURING THE WEEKEND AS A SHORT
WAVE TROUGH AMPLIFIES AND BECOMES A CLOSED LOW OVER THE LOWER
MISSISSIPPI VALLEY. THE ASSOCIATED UPPER-LEVEL TROUGH WILL DIG
INTO THE CENTRAL GULF AND MOVES SLOWLY EWD.

CARIBBEAN SEA...
THE REMNANTS OF A FRONTAL BOUNDARY CONTINUES TO PRODUCE A BAND
OF SHOWERS WITH ISOLATED TSTMS FROM THE WINDWARD PASSAGE/E CUBA
TO OVER JAMAICA AND NORTHERN HONDURAS. AN EARLIER ASCAT SHOWED
MODERATE TO STRONG NE WINDS OF 20 TO 25 KT OVER THE NW CARIBBEAN
BEHIND THE REMNANTS OF THE FRONT. SCATTERED MODERATE CONVECTION
IS OVER THE SW CARIBBEAN WHILE ISOLATED SHOWERS DOT THE
REMAINDER OF THE CARIBBEAN USHERED IN ON MODERATE TO STRONG
EASTERLY TRADE WINDS. AN AREA OF LOW LEVEL MOISTURE WITH
EMBEDDED SHOWERS IS MOVING WWD ACROSS THE NE CARIBBEAN AFFECTING
THE NORTHERN LEEWARD ISLANDS AND THE VIRGIN ISLANDS. THIS
ACTIVITY WILL REACH EASTERN PUERTO RICO LATER THIS EVENING. IN
THE UPPER LEVELS...THE BASIN IS DOMINATED BY AN UPPER RIDGE
CENTERED OVER THE GULF OF HONDURAS. WLY WINDS ON THE NORTHERN
SIDE OF THIS RIDGE ARE NOTED OVER CUBA. THIS RIDGE IS SUPPORTING
CONVECTION ALONG THE REMNANTS OF THE FRONT AND OVER THE SW
CARIBBEAN. SCATTERED MODERATE CONVECTION IS ALSO OVER PARTS OF
PANAMA AND COSTA RICA LIKELY DUE TO THE CLOSE PROXIMITY OF THE
EPAC ITCZ.

ATLANTIC OCEAN...
A DEEP LAYERED TROUGH PERSISTS OVER THE WRN ATLC WHILE THE RIDGE
OVER THE CARIBBEAN SEA EXTENDS NE THROUGH THE N LEEWARD ISLANDS
INTO THE CENTRAL ATLC. A BAND OF MULTILAYERED CLOUDS WITH
EMBEDDED SHOWERS LIES BETWEEN THESE TWO UPPER-LEVEL FEATURES AND
EXTENDS FROM EASTERN CUBA/WINDWARD PASSAGE ALL THE WAY NE TO
BEYOND 32N54W. AT THE SURFACE...A FRONTAL BOUNDARY AND A SFC
TROUGH IS ASSOCIATED WITH THIS BAND OF CLOUDS. HIGH PRES
SITUATED OVER THE CAROLINAS EXTENDS A RIDGE OVER THE W ATLC AND
THE BAHAMAS. BROKEN COLD AIR STRATOCUMULUS CLOUDS AND NE WINDS
OF 20 TO 25 KT COVER THIS AREA. THESE WINDS ARE ADVECTING
PATCHES OF LOW LEVEL MOISTURE WITH ISOLATED SHOWERS ACROSS
FLORIDA. A NARROW UPPER-LEVEL TROUGH IS IN THE CENTRAL ATLC
EXTENDING FROM NEAR 25N45W INTO THE TROPICS TO NEAR 8N50W.
SUBSIDENCE/DRY AIR BEHIND THIS UPPER TROUGH DOMINATES THE
TROPICS BETWEEN 50W AND THE LESSER ANTILLES. A BROAD UPPER-LEVEL
TROUGH ENTERS THE FORECAST AREA THROUGH THE MADEIRA/CANARY
ISLANDS. THE ATTENDANT COLD FRONT IS APPROACHING THE CANARY
ISLANDS WHERE WLY WINDS OF 15 TO 20 KT ARE BLOWING. AN E/W UPPER
RIDGE COVERS THE REMAINDER OF THE TROPICAL ATLC ANCHORED OFF THE
COAST OF W AFRICA NEAR 11N23W. THE UPPER DIFFLUENCE ASSOCIATED
WITH THIS UPPER RIDGE IS AIDING IN SUPPORTING THE CONVECTION
ASSOCIATED WITH THE SURFACE TROUGHS EMBEDDED WITHIN THE ITCZ.

OF NOTE...NOVEMBER IS THE LAST MONTH OF THE ATLANTIC HURRICANE
SEASON. SO FAR...FIFTEEN NAMED STORMS HAVE DEVELOPED...OF WHICH
SEVEN BECAME HURRICANES...WITH FOUR OF THE HURRICANES ATTAINING
MAJOR HURRICANE STATUS. IN ADDITION...A SHORT LIFE TROPICAL
DEPRESSION FORMED IN OCTOBER. THE MOST POWERFUL HURRICANES SEEN
THIS SEASON ARE GUSTAV AND IKE...BOTH CAT 4 ON THE SAFFIR
SIMPSON SCALE.

$$
GR





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